How To Develop A Flutter Plugin: A Comprehensive Guide

How To Develop A Flutter Plugin: A Comprehensive Guide

Flutter is a UI toolkit that allows you to create natively compiled applications for mobile, web, and desktop from a single codebase. One powerful aspect of Flutter is the ability to create plugins that enable developers to write native code that can then be called from their Dart code. In this guide, we'll be focusing on how to develop a Flutter plugin.

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What are Flutter Plugins?

Flutter plugins are Dart packages that provide additional functionality not covered by the core libraries. They grant access to native platform APIs and services that aren't available in Dart or Flutter by default. Flutter plugin development is crucial because it allows developers to interact with native platform-specific features.

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Dive into Flutter Plugin Development

In setting out to create your own plugin, there's one key concept you should understand: the relationship between Dart code and platform-specific code. Flutter plugins bridge the gap between the Dart virtual machine and the platform APIs by using platform channels.

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Why are Flutter Plugins Important?

Flutter plugins extend the capabilities of Flutter apps by allowing them to tap into native functionality. This means that a Flutter app developed with plugins can handle complex tasks like payment processing or file system access, making the app more feature-rich and competitive.

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What is a Platform Channel?

A platform channel is a medium through which your Flutter app (Dart code) communicates with the native code. The channel connects the Dart UI to the platform's native APIs, giving your Dart file access to the platform-specific functionality. Platform channels are fundamental to the Flutter plugin architecture.

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Setting up the Development Environment: Best Plugin for Flutter in Android Studio

Before you can start developing your own Flutter plugin, it's necessary to get your development environment all set up.

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Flutter Plugin Development Requirements

Creating plugins requires Flutter SDK, an integrated development environment (IDE) like Android Studio, and a familiarity with the language for the platforms you plan to support (such as Java or Kotlin for Android, and Swift or Objective-C for iOS).

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Installing the Flutter SDK and Android Studio

• First, download and install Flutter SDK.
• Next, install Android Studio, which is a great IDE not only for Android development but also for Flutter development.
• Lastly, install the Flutter and Dart plugins in Android Studio to get added support for these languages.

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Setting up the Flutter Plugin in Android Studio

Setting up the Flutter plugin in Android Studio is a straightforward process.

Here's how you can do it:

1. In Android Studio, open plugin preferences (Preferences>Plugins on macOS, File>Settings>Plugins on Windows & Linux).
2. Select Marketplace, select the Flutter plugin and click Install.
3. Click Yes when prompted to install the Dart plugin.
4. Restart when prompted.

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Understanding Federated Plugins

As you venture deeper into Flutter plugin development, you'll encounter a term known as federated plugins.

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Explanation of Federated Plugins

Federated plugins are a method of separating platform support into independent packages. A federated plugin, for example, can use one package for iOS, another for Android, another for web, and even another for an IoT device such as a car. Federated plugins ensure a more effective and efficient approach to platform-specific code maintenance.

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Advantages of Federated Plugins

One substantial advantage of federated plugins is allowing different developers to extend an existing plugin to work on platforms they are most familiar with. This means that a domain expert can focus on an implementation for a specific platform, making the plugin more robust, performant, and secure.

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Structure of Federated Plugins

Understanding the structure of federated plugins is important while developing your own federated plugin.

• App-Facing Package - This is the package your app will interact with. It defines the API your Flutter app will use and depends on the platform interface package.
• Platform Package(s) - Here are where the platform-specific bits of code go. These are the packages that handle the platform-specific code interaction.
• Platform Interface Package - This package bridges the gap between the app-facing package and platform package(s). The interface ensures uniform functionality across platforms.

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Endorsed and Non-endorsed Federated Plugins

You can have two types of federated plugins – endorsed and non-endorsed ones. An endorsed plugin means the original author has included your implementation as an endorsed platform, while a non-endorsed one means your implementation hasn't been added by the original plugin author.

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Developing a Unique Flutter VR Plugin

With the ever-evolving innovation in technology, VR (Virtual Reality) is making waves across various industries. Let's dive into developing a unique Flutter VR Plugin.

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Benefits of VR (Virtual Reality) Plugins

VR plugins have a unique role in enhancing applications with 3D front-end experiences and can make your application stand out. They can support complex, real-time interactions with 3D data, amplifying user engagements in your Flutter app to the next level.

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Essential Activity and UI Components for Flutter VR Plugin

Firstly, you need to create a VR activity. This VR activity is where all the major functionality related to VR is going to happen. Here's an example on how to create a VR activity:

After creating and setting up your VR activity, you need to create the user interface (UI) components that handle the VR functionality of your Flutter app. These can include view controllers, renderers, motion handlers, and other essential components.

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Plugin Classification: Specifying a Plugin's Supported Platforms

Plugin classification is vitally important. When you develop a Flutter plugin, you need to specify which platforms the plugin will support.

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How to Map Platform Support in pubspec.yaml

As part of the Flutter plugin development process, you'll specify the platforms your plugin supports by adding keys to the platforms map in the pubspec.yaml file. Here's an example of how it would look for a plugin that supports Android and iOS:

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Example: Mapping for macOS and Web Support

Further extending the plugin's compatibility, we can add support for macOS and Web. Here's an example of how it should look in the pubspec.yaml file:

In the snippet above, you can see the plugin supports the Android, iOS, macOS, and web platforms (android, ios, macos, web).

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Deep-Diving into Federated Platform Packages

Now we will dive deeper into the structure and implementation of federated platform packages. Such packages reside at the core of the federated plugins, underpinning their capabilities.

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Structure and Implementation

A federated platform package follows a similar structure to a basic plugin package. However, they contain an additional implements entry to indicate which app-facing package it implements. Here's an example:

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Endorsed Implementations

A platform package can be endorsed by adding a dependence on it and including it as a default_package in the platforms: map.

In this example, "hello_windows" is an endorsed implementation of the "hello" plugin, and it is also added as a dependency in the pubspec.yaml file.

As shown, an app-facing package can have some platforms implemented within the package, and others in endorsed federated implementations. This allows more flexibility and opportunities for multiple developers to contribute their platform-specific expertise.

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Explore Shared iOS and MacOS Implementations

In the world of Flutter plugin development, it's common to encounter scenarios where a plugin necessitates the same or similar functionality on iOS and macOS platforms.

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Advantages of SharedDarwinSource

Flutter provides one unique functionality to satisfy this need: sharedDarwinSource. Many frameworks support both iOS and macOS with similar or almost equivalent APIs, allowing some plugins to be developed for both platforms using the same codebase.

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Configuration for SharedDarwinSource

We can configure iOS and macOS to use a shared folder, named dartwin, for all code and resources. Here's an example of how it should look in the pubspec.yaml file:

In this configuration, you will observe that both iOS and macOS utilize the same dartwin directory for all code and resources. This simplifies code maintenance by allowing a single codebase to serve both platform implementations.

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Step-by-Step Guide to Develop a Flutter Plugin

Now that we've covered all the fundamentals, it's time to jump into the practical aspect and learn how to develop a Flutter plugin.

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Step 1: Creating the Plugin Package

This is the preliminary and a significant step in the Flutter plugin development process. In this step, you'll be creating a plugin package using flutter create:

Here, the plugin package named 'hello' is created, which would support Android, iOS, Linux, macOS, and Windows platforms. The Kotlin language is specified for the Android platform.

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Step 2: Implementing the Flutter Plugin

Upon the successful creation of the plugin, the next step would be its implementation.

• Define the Package API (.dart): The API of the plugin package is defined in Dart code within the 'lib' folder.

• Add Android Platform Code (.kt/.java): You can add the Android specific code in src/main/kotlin/com.example.hello/HelloPlugin folder.
• Add iOS Platform Code (.swift/.h+.m): The iOS specific code can be written under iOS/Classes. This code will implement the iOS platform-specific functionality for your Flutter plugin.

At this point, you are all set with the initial setup and have a broad understanding of how to develop a Flutter plugin.

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Dart Platform Implementations

Building upon the foundation we've created, let's now explore the role Dart plays, particularly when mixed with other platform-specific languages.

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Overview of Dart Platform Implementations

In many cases, non-web platform implementations only use the platform-specific implementation language, as shown in our earlier sections. However, platform implementations can also use platform-specific Dart as well.

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Dart-only Platform Implementations

In some cases, some platforms can be implemented entirely in Dart (for example, using FFI). Let's modify our previous 'hello_windows' example for a Dart-only implementation:

In the above configuration, your Dart implementation replaces the previous C++ Windows code.

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Hybrid Platform Implementations

In some scenarios, platform implementations can use both Dart and a platform-specific language, forming a hybrid implementation:

In the above configuration, the Dart plugin class 'HelloPluginWindows' works in tandem with the C++ class 'HelloPlugin'.

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Testing your Flutter Plugin

Last but certainly not least, we'll address an essential part of any development process - testing.

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Importance of Testing in Flutter Plugin Development

Testing your Flutter plugin is a crucial step in the development process. This ensures that your functionalities work as expected and don't regress as you make changes to your code, providing you with confidence that your plugin does what it's intended to do.

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Wrapping Up

This comprehensive guide walked you through every facet of Flutter plugin development. We dissected the process of creating a plugin package, understanding federated plugins, talked about incorporating VR functionality, and touched upon specifying platform support in your plugin. We dived into Dart platform implementations and seamlessly connected Dart code with platform-specific code. Lastly, we highlighted the enormous importance of regularly testing your plugin package. With these insights, we believe you're now well-prepared to handle Flutter and Dart complexities, presenting a great opportunity to upgrade your apps to deliver richer, more versatile user experiences. Happy Fluttering!